Psychology is the science of behavior and mental processes. Its immediate goal is
to understand individuals and groups by both establishing general principles and
researching specific cases. For many, the ultimate goal of psychology is to benefit
society. In this field, a professional practitioner or researcher is called a psychologist,
and can be classified as a social scientist, behavioral scientist, or cognitive
scientist. Psychologists attempt to understand the role of mental functions in individual
and social behavior, while also exploring the physiological and neurobiological
processes that underlie certain functions and behaviors. Psychologists explore such
concepts as perception, cognition, attention, emotion, phenomenology, motivation,
brain functioning, personality, behavior, and interpersonal relationships. Some,
especially depth psychologists, also consider the unconscious mind.a Psychologists
employ empirical methods to infer causal and correlational relationships between
psychosocial variables. In addition, or in opposition, to employing empirical and
deductive methods, some—especially clinical and counseling psychologists—at times
rely upon symbolic interpretation and other inductive techniques. Psychology incorporates
research from the social sciences, natural sciences, and humanities, such as philosophy.

While psychological knowledge is often applied to the assessment and treatment of
mental health problems, it is also applied to understanding and solving problems
in many different spheres of human activity. Although the majority of psychologists
are involved in some kind of therapeutic role (clinical, counseling, and school
positions), many do scientific research on a wide range of topics related to mental
processes and behavior (typically in university psychology departments) or teach
such knowledge in academic settings; and some are employed in industrial and organizational
settings, and in other areas such as human development and aging, sports, health,
the media, law, and forensics.

Clinical psychologists work with individuals,
children, families, couples, or small groups.

Etymology

The word psychology literally means, according to "Webster's Dictionary", "the study
of the soul" ( meaning "breath", "spirit", or "soul"; and --logia, translated as
"study of" or "research"). The Latin word psychologia was first used by the Croatian
humanist and Latinist Marko Marulić in his book, Psichiologia de ratione animae
humanae in the late 15th century or early 16th century. The earliest known reference
to the word psychology in English was by Steven Blankaart in 1694 in The Physical
Dictionary which refers to "Anatomy, which treats of the Body, and Psychology, which
treats of the Soul."

History

The study of psychology in a philosophical context dates back to the ancient civilizations
of Egypt, Greece, China, India, and Persia. Historians point to the writings of
ancient Greek philosophers, such as Thales, Plato, and Aristotle (especially in
his De Anima treatise), as the first significant body of work in the West to be
rich in psychological thought.

Structuralism

German physician Wilhelm Wundt is credited with introducing psychological discovery
into a laboratory setting. Known as the "father of experimental psychology", he
founded the first psychological laboratory, at Leipzig University, in 1879. Wundt
focused on breaking down mental processes into the most basic components. Edward
Titchener was another major structuralist thinker.

Functionalism

Functionalism formed as a reaction to the theories of the structuralist school of
thought and was heavily influenced by the work of the American philosopher, scientist
and psychologist William James. James felt that psychology should have practical
value, and that psychologists should find out how the mind can function to a person's
benefit. In his book, Principles of Psychology, published in 1890, he laid the foundations
for many of the questions that psychologists would explore for years to come. Other
major functionalist thinkers included John Dewey and Harvey Carr.

Other 19th-century contributors to the field include the German psychologist Hermann
Ebbinghaus, a pioneer in the experimental study of memory, who developed quantitative
models of learning and forgetting[16] at the University of Berlin; and the Russian-Soviet
physiologist Ivan Pavlov, who discovered in dogs a learning process that was later
termed "classical conditioning" and applied to human beings.

Starting in the 1950s, the experimental techniques set forth by Wundt, James, Ebbinghaus,
and others would be reiterated as experimental psychology became increasingly cognitive—concerned
with information and its processing—and, eventually, constituted a part of the wider
cognitive science. In its early years, this development had been seen as a "revolution",
as it both responded to and reacted against strains of thought—including psychodynamics
and behaviorism—that had developed in the meantime.

Psychoanalysis

From the 1890s until his death in 1939, the Austrian physician Sigmund Freud developed
psychoanalysis, a method of investigation of the mind and the way one thinks; a
systematized set of theories about human behavior; and a form of psychotherapy to
treat psychological or emotional distress, especially unconscious conflict. Freud's
psychoanalytic theory was largely based on interpretive methods, introspection and
clinical observations. It became very well known, largely because it tackled subjects
such as sexuality, repression, and the unconscious mind as general aspects of psychological
development. These were largely considered taboo subjects at the time, and Freud
provided a catalyst for them to be openly discussed in polite society. Clinically,
Freud helped to pioneer the method of free association and a therapeutic interest
in dream interpretation.

Freud had a significant influence on Swiss psychiatrist Carl Jung, whose analytical
psychology became an alternative form of depth psychology. Other well-known psychoanalytic
scholars of the mid-20th century included psychoanalysts, psychologists, psychiatrists,
and philosophers. Among these thinkers were Erik Erikson, Melanie Klein, D.W. Winnicott,
Karen Horney, Erich Fromm, John Bowlby, and Sigmund Freud's daughter, Anna Freud.
Throughout the 20th century, psychoanalysis evolved into diverse schools of thought,
most of which may be classed as Neo-Freudian.b Psychoanalytic theory and therapy
were criticized by psychologists such as Hans Eysenck, and by philosophers including
Karl Popper. Popper, a philosopher of science, argued that psychoanalysis had been
misrepresented as a scientific discipline, whereas Eysenck said that psychoanalytic
tenets had been contradicted by experimental data. By the 20th century, psychology
departments in American universities had become scientifically oriented, marginalizing
Freudian theory and dismissing it as a "desiccated and dead" historical artifact.
Meanwhile, however, researchers in the emerging field of neuro-psychoanalysis defended
some of Freud's ideas on scientific grounds,c while scholars of the humanities maintained
that Freud was not a "scientist at all, but ... an interpreter."

Behaviorism

In the United States, behaviorism became the dominant school of thought during the
1950s. Behaviorism is a discipline that was established in the early 20th century
by John B. Watson, and embraced and extended by Edward Thorndike, Clark L. Hull,
Edward C. Tolman, and later B.F. Skinner. Theories of learning emphasized the ways
in which people might be predisposed, or conditioned, by their environments to behave
in certain ways.

Classical conditioning was an early behaviorist model. It posited that behavioral
tendencies are determined by immediate associations between various environmental
stimuli and the degree of pleasure or pain that follows. Behavioral patterns, then,
were understood to consist of organisms' conditioned responses to the stimuli in
their environment. The stimuli were held to exert influence in proportion to their
prior repetition or to the previous intensity of their associated pain or pleasure.
Much research consisted of laboratory-based animal experimentation, which was increasing
in popularity as physiology grew more sophisticated.

Skinner's behaviorism shared with its predecessors a philosophical inclination toward
positivism and determinism.He believed that the contents of the mind were not open
to scientific scrutiny and that scientific psychology should emphasize the study
of observable behavior. He focused on behavior–environment relations and analyzed
overt and covert (i.e., private) behavior as a function of the organism interacting
with its environment. Behaviorists usually rejected or deemphasized dualistic explanations
such as "mind" or "consciousness"; and, in lieu of probing an "unconscious mind"
that underlies unawareness, they spoke of the "contingency-shaped behaviors" in
which unawareness becomes outwardly manifest.

Among the behaviorists' most famous creations are John B. Watson's Little Albert
experiment, which applied classical conditioning to the developing human child,
and Skinner's notion of operant conditioning, which acknowledged that human agency
could affect patterns and cycles of environmental stimuli and behavioral responses.

Linguist Noam Chomsky's critique of the behaviorist model of language acquisition
is widely regarded as a key factor in the decline of behaviorism's prominence. Martin
Seligman and colleagues discovered that the conditioning of dogs led to outcomes
("learned helplessness") that opposed the predictions of behaviorism. But Skinner's
behaviorism did not die, perhaps in part because it generated successful practical
applications. The fall of behaviorism as an overarching model in psychology, however,
gave way to a new dominant paradigm: cognitive approaches.

Humanism

Humanistic psychology was developed in the 1950s in reaction to both behaviorism
and psychoanalysis.By using phenomenology, intersubjectivity and first-person categories,
the humanistic approach sought to glimpse the whole person—not just the fragmented
parts of the personality or cognitive functioning. Humanism focused on fundamentally
and uniquely human issues, such as individual free will, personal growth, self-actualization,
self-identity, death, aloneness, freedom, and meaning. The humanistic approach was
distinguished by its emphasis on subjective meaning, rejection of determinism, and
concern for positive growth rather than pathology.[citation needed] Some of the
founders of the humanistic school of thought were American psychologists Abraham
Maslow, who formulated a hierarchy of human needs, and Carl Rogers, who created
and developed client-centered therapy. Later, positive psychology opened up humanistic
themes to scientific modes of exploration.

Gestalt

Wolfgang Kohler, Max Wertheimer and Kurt Koffka co-founded the school of Gestalt
psychology. This approach is based upon the idea that individuals experience things
as unified wholes. This approach to psychology began in Germany and Austria during
the late 19th century in response to the molecular approach of structuralism. Rather
than breaking down thoughts and behavior to their smallest element, the Gestalt
position maintains that the whole of experience is important, and the whole is different
than the sum of its parts.

Gestalt psychology should not be confused with the Gestalt therapy of Fritz Perls,
which is only peripherally linked to Gestalt psychology.

Existentialism

In the 1950s and 1960s, largely influenced by the work of German philosopher Martin
Heidegger and Danish philosopher Søren Kierkegaard, psychoanalytically trained American
psychologist Rollo May pioneered an existential branch of psychology, which included
existential psychotherapy, a method of therapy that operates on the belief that
inner conflict within a person is due to that individual's confrontation with the
givens of existence.

Existential psychologists differed from others often classified as humanistic in
their comparatively neutral view of human nature and in their relatively positive
assessment of anxiety.[33] Existential psychologists emphasized the humanistic themes
of death, free will, and meaning, suggesting that meaning can be shaped by myths,
or narrative patterns,[34] and that it can be encouraged by an acceptance of the
free will requisite to an authentic, albeit often anxious, regard for death and
other future prospects.

Austrian existential psychiatrist and Holocaust survivor Viktor Frankl drew evidence
of meaning's therapeutic power from reflections garnered from his own internment,[35]
and he created a variety of existential psychotherapy called logotherapy, a type
of existentialist analysis that focuses on a will to meaning (in one's life), as
opposed to Adler's Nietzschean doctrine of will to power or Freud's will to pleasure.

In addition to May and Frankl, Swiss psychoanalyst Ludwig Binswanger and American
psychologist George Kelly may be said to belong to the existential school.

Cognitivism

Cognitive psychology is the branch of psychology that studies mental processes including
how people think, perceive, remember, and learn. As part of the larger field of
cognitive science, this branch of psychology is related to other disciplines including
neuroscience, philosophy, and linguistics.

Noam Chomsky helped to ignite a "cognitive revolution" in psychology when he criticized
the behaviorists' notions of "stimulus", "response", and "reinforcement", arguing
that such ideas—which Skinner had borrowed from animal experiments in the laboratory—could
be applied to complex human behavior, most notably language acquisition, in only
a superficial and vague manner. The postulation that humans are born with the instinct
or "innate facility" for acquiring language posed a challenge to the behaviorist
position that all behavior, including language, is contingent upon learning and
reinforcement.[38] Social learning theorists, such as Albert Bandura, argued that
the child's environment could make contributions of its own to the behaviors of
an observant subject.

Meanwhile, accumulating technology helped to renew interest and belief in the mental
states and representations—i.e., the cognition—that had fallen out of favor with
behaviorists. English neuroscientist Charles Sherrington and Canadian psychologist
Donald O. Hebb used experimental methods to link psychological phenomena with the
structure and function of the brain. With the rise of computer science and artificial
intelligence, analogies were drawn between the processing of information by humans
and information processing by machines. Research in cognition had proven practical
since World War II, when it aided in the understanding of weapons operation. By
the late 20th century, though, cognitivism had become the dominant paradigm of mainstream
psychology, and cognitive psychology emerged as a popular branch.

Assuming both, that the covert mind should be studied and that the scientific method
should be used to study it, cognitive psychologists set such concepts as subliminal
processing and implicit memory in place of the psychoanalytic unconscious mind or
the behavioristic contingency-shaped behaviors. Elements of behaviorism and cognitive
psychology were synthesized to form the basis of cognitive behavioral therapy, a
form of psychotherapy modified from techniques developed by American psychologist
Albert Ellis and American psychiatrist Aaron T. Beck. Cognitive psychology was subsumed
along with other disciplines, such as philosophy of mind, computer science, and
neuroscience, under the cover discipline of cognitive science.

Biopsychosocial model

The biopsychosocial model is an integrated perspective toward understanding consciousness,
behavior, and social interaction. It assumes that any given behavior or mental process
affects and is affected by dynamically interrelated biological, psychological, and
social factors. The psychological aspect refers to the role that cognition and emotions
play in any given psychological phenomenon—for example, the effect of mood or beliefs
and expectations on an individual's reactions to an event. The biological aspect
refers to the role of biological factors in psychological phenomena—for example,
the effect of the prenatal environment on brain development and cognitive abilities,
or the influence of genes on individual dispositions. The socio-cultural aspect
refers to the role that social and cultural environments play in a given psychological
phenomenon—for example, the role of parental or peer influence in the behaviors
or characteristics of an individual.

Discursive psychology

Discursive psychology was developed in the 1990s by Jonathan Potter and Derek Edwards.
It examines how psychological phenomena are created, made relevant and put to use
in discourse, verbal interaction and everyday talk. It is opposed to cognitivist
approaches.

Critical psychology

Critical psychology is aimed at evaluating mainstream psychology and attempts to
apply psychology in more progressive ways, often looking towards social change as
a means of preventing and treating psychopathology. One of critical psychology's
main criticisms of conventional psychology is how it ignores the way power differences
between social classes and groups can affect the mental and physical well-being
of individuals or groups of people. Contributors to the field include Klaus Holzkamp
and Ian Parker. Key elements within critical psychology include the study of power
relations, situated knowledge, and the dualisms of the self and the agency, and
the individual and the social.

Subfields

Further information: List of psychology topics and List of psychology disciplines

Psychology encompasses a vast domain, and includes many different approaches to
the study of mental processes and behavior.

Biological

Biological psychology or behavioral neuroscience is the study of the biological
substrates of behavior and mental processes. There are different specialties within
behavioral neuroscience. For example, physiological psychologists use animal models
(typically rats) to study the neural, genetic, and cellular mechanisms that underlie
specific behaviors such as learning and memory and fear responses.[42] Cognitive
neuroscientists investigate the neural correlates of psychological processes in
humans using neural imaging tools, and neuropsychologists conduct psychological
assessments to determine, for instance, specific aspects and extent of cognitive
deficit caused by brain damage or disease.

Clinical

Clinical psychology includes the study and application of psychology for the purpose
of understanding, preventing, and relieving psychologically-based distress or dysfunction
and to promote subjective well-being and personal development. Central to its practice
are psychological assessment and psychotherapy, although clinical psychologists
may also engage in research, teaching, consultation, forensic testimony, and program
development and administration.[43] Some clinical psychologists may focus on the
clinical management of patients with brain injury—this area is known as clinical
neuropsychology. In many countries, clinical psychology is a regulated mental health
profession.

The work performed by clinical psychologists tends to be influenced by various therapeutic
approaches, all of which involve a formal relationship between professional and
client (usually an individual, couple, family, or small group). The various therapeutic
approaches and practices are associated with different theoretical perspectives
and employ different procedures intended to form a therapeutic alliance, explore
the nature of psychological problems, and encourage new ways of thinking, feeling,
or behaving. Four major theoretical perspectives are psychodynamic, cognitive behavioral,
existential–humanistic, and systems or family therapy. There has been a growing
movement to integrate the various therapeutic approaches, especially with an increased
understanding of issues regarding culture, gender, spirituality, and sexual-orientation.
With the advent of more robust research findings regarding psychotherapy, there
is evidence that most of the major therapies are about of equal effectiveness, with
the key common element being a strong therapeutic alliance.[44][45] Because of this,
more training programs and psychologists are now adopting an eclectic therapeutic
orientation.

On a broader level, cognitive science is an interdisciplinary enterprise of cognitive
psychologists, cognitive neuroscientists, researchers in artificial intelligence,
linguists, human–computer interaction, computational neuroscience, logicians and
social scientists. Computational models are sometimes used to simulate phenomena
of interest. Computational models provide a tool for studying the functional organization
of the mind whereas neuroscience provides measures of brain activity.

Comparative

Comparative psychology refers to the study of the behavior and mental life of animals
other than human beings. It is related to disciplines outside of psychology that
study animal behavior such as ethology. Although the field of psychology is primarily
concerned with humans, the behavior and mental processes of animals is also an important
part of psychological research. This being either as a subject in its own right
(e.g., animal cognition and ethology) or with strong emphasis about evolutionary
links, and somewhat more controversially, as a way of gaining an insight into human
psychology. This is achieved by means of comparison or via animal models of emotional
and behavior systems as seen in neuroscience of psychology (e.g., affective neuroscience
and social neuroscience).

Developmental

Mainly focusing on the development of the human mind through the life span, developmental
psychology seeks to understand how people come to perceive, understand, and act
within the world and how these processes change as they age. This may focus on intellectual,
cognitive, neural, social, or moral development. Researchers who study children
use a number of unique research methods to make observations in natural settings
or to engage them in experimental tasks. Such tasks often resemble specially designed
games and activities that are both enjoyable for the child and scientifically useful,
and researchers have even devised clever methods to study the mental processes of
small infants. In addition to studying children, developmental psychologists also
study aging and processes throughout the life span, especially at other times of
rapid change (such as adolescence and old age). Developmental psychologists draw
on the full range of psychological theories to inform their research.

Educational and school

Educational psychology is the study of how humans learn in educational settings,
the effectiveness of educational interventions, the psychology of teaching, and
the social psychology of schools as organizations. The work of child psychologists
such as Lev Vygotsky, Jean Piaget, Bernard Luskin and Jerome Bruner has been influential
in creating teaching methods and educational practices. Educational psychology is
often included in teacher education programs, in places such as North America, Australia,
and New Zealand.

School psychology combines principles from educational psychology and clinical psychology
to understand and treat students with learning disabilities; to foster the intellectual
growth of gifted students; to facilitate prosocial behaviors in adolescents; and
otherwise to promote safe, supportive, and effective learning environments. School
psychologists are trained in educational and behavioral assessment, intervention,
prevention, and consultation, and many have extensive training in research.

Evolutionary

Evolutionary psychology examines psychological traits—such as memory, perception,
or language—from a modern evolutionary perspective. It seeks to identify which human
psychological traits are evolved adaptations, that is, the functional products of
natural selection or sexual selection. Evolutionary psychologists suggest that psychological
adaptations evolved to solve recurrent problems in human ancestral environments.
By focusing on the evolution of psychological traits and their adaptive functions,
it offers complementary explanations for the mostly proximate or developmental explanations
developed by other areas of psychology (that is, it focuses mostly on ultimate or
"why?" questions, rather than proximate or "how?" questions).

Industrial–organizational

Industrial and organizational psychology (I–O) applies psychological concepts and
methods to optimize human potential in the workplace. Personnel psychology, a subfield
of I–O psychology, applies the methods and principles of psychology in selecting
and evaluating workers. I–O psychology's other subfield, organizational psychology,
examines the effects of work environments and management styles on worker motivation,
job satisfaction, and productivity.

Personality

Personality psychology is concerned to enduring patterns of behavior, thought, and
emotion in individuals, commonly referred to as personality. Theories of personality
vary across different psychological schools and orientations. They carry different
assumptions about such issues as the role of the unconscious and the importance
of childhood experience. According to Freud, personality is based on the dynamic
interactions of the id, ego, and super-ego. Trait theorists, in contrast, attempt
to analyze personality in terms of a discrete number of key traits by the statistical
method of factor analysis. The number of proposed traits has varied widely. An early
model proposed by Hans Eysenck suggested that there are three traits that comprise
human personality: extraversion–introversion, neuroticism, and psychoticism. Raymond
Cattell proposed a theory of 16 personality factors. The "Big Five", or Five Factor
Model, proposed by Lewis Goldberg, currently has strong support among trait theorists.

Social

Social psychology is the study of how humans think about each other and how they
relate to each other. Social psychologists study such topics as the influence of
others on an individual's behavior (e.g. conformity, persuasion), and the formation
of beliefs, attitudes, and stereotypes about other people. Social cognition fuses
elements of social and cognitive psychology in order to understand how people process,
remember, and distort social information. The study of group dynamics reveals information
about the nature and potential optimization of leadership, communication, and other
phenomena that emerge at least at the microsocial level. In recent years, many social
psychologists have become increasingly interested in implicit measures, mediational
models, and the interaction of both person and social variables in accounting for
behavior. The study of human society, is therefore a potentially valuable source
of information about the causes of psychiatric disorder. Some of the sociological
concepts applied to psychiatric disorders are the social role, sick role, social
class, life event, culture, migration, social and total institution.

Positive

Positive psychology derives from Maslow's humanistic psychology. Positive psychology
is a discipline that utilizes evidence-based scientific methods to study factors
that contribute to human happiness and strength. Different from clinical psychology,
positive psychology is concerned with improving the mental well-being of healthy
clients. Positive psychological interventions now have received tentative support
for their beneficial effects on clients. In 2010 Clinical Psychological Review published
a special issue devoted to positive psychological interventions, such as gratitude
journaling and the physical expression of gratitude. There is, however, a need for
further research on the effects of interventions. Positive psychological interventions
have been limited in scope but their effects are thought to be superior to that
of placebos, especially with regard to helping people with body image problems.

Research methods

Psychology tends to be eclectic, drawing on knowledge from other fields to help
explain and understand psychological phenomena. Additionally, psychologists make
extensive use of the three modes of inference that were identified by C.S. Peirce:
deduction, induction, and abduction (hypothesis generation). While often employing
deductive–nomological reasoning, they also rely on inductive reasoning to generate
explanations. For example, evolutionary psychologists attempt to explain psychological
traits—such as memory, perception, or language—as adaptations, that is, as the functional
products of natural selection or sexual selection.

Psychologists may conduct basic research aiming for further understanding in a particular
area of interest in psychology, or conduct applied research to solve problems in
the clinic, workplace or other areas. Masters level clinical programs aim to train
students in both research methods and evidence-based practice. Professional associations
have established guidelines for ethics, training, research methodology and professional
practice. In addition, depending on the country, state or region, psychological
services and the title "psychologist" may be governed by statute and psychologists
who offer services to the public are usually required to be licensed.

Qualitative and quantitative research

Research in most areas of psychology is conducted in accord with the standards of
the scientific method. Psychological researchers seek the emergence of theoretically
interesting categories and hypotheses from data, using qualitative or quantitative
methods (or both).

Qualitative psychological research methods include interviews, first-hand observation,
and participant observation. Creswell (2003) identifies five main possibilities
for quantitative research, including narrative, phenomenology, ethnography, case
study and grounded theory. Qualitative researchers[55] sometimes aim to enrich interpretations
or critiques of symbols, subjective experiences, or social structures. Similar hermeneutic
and critical aims have also been served by "quantitative methods", as in Erich Fromm's
study of Nazi voting[citation needed] or Stanley Milgram's studies of obedience
to authority.

Quantitative psychological research lends itself to the statistical testing of hypotheses.
Quantitatively oriented research designs include the experiment, quasi-experiment,
cross-sectional study, case-control study, and longitudinal study. The measurement
and operationalization of important constructs is an essential part of these research
designs. Statistical methods include the Pearson product–moment correlation coefficient,
the analysis of variance, multiple linear regression, logistic regression, structural
equation modeling, and hierarchical linear modeling.

Controlled experiments

Experimental psychological research is conducted in a laboratory under controlled
conditions. This method of research relies on the application of the scientific
method to understand behavior. Experimenters use several types of measurements,
including rate of response, reaction time, and various psychometric measurements.
Experiments are designed to test specific hypotheses (deductive approach) or evaluate
functional relationships (inductive approach). A true experiment with random allocation
of subjects to conditions allows researchers to infer causal relationships between
different aspects of behavior and the environment. In an experiment, one or more
variables of interest are controlled by the experimenter (independent variable)
and another variable is measured in response to different conditions (dependent
variable). Experiments are one of the primary research methods in many areas of
psychology, particularly cognitive/psychonomics, mathematical psychology, psychophysiology
and biological psychology/cognitive neuroscience.

Experiments on humans have been put under some controls, namely informed and voluntary
consent. After World War II, the Nuremberg Code was established, because of Nazi
abuses of experimental subjects. Later, most countries (and scientific journals)
adopted the Declaration of Helsinki. In the U.S., the National Institutes of Health
established the Institutional Review Board in 1966, and in 1974 adopted the National
Research Act (HR 7724). All of these measures encouraged researchers to obtain informed
consent from human participants in experimental studies. A number of influential
studies led to the establishment of this rule; such studies included the MIT and
Fernald School radioisotope studies, the Thalidomide tragedy, the Willowbrook hepatitis
study, and Stanley Milgram's studies of obedience to authority.

Survey questionnaires

Statistical surveys are used in psychology for measuring attitudes and traits, monitoring
changes in mood, checking the validity of experimental manipulations, and for a
wide variety of other psychological topics. Most commonly, psychologists use paper-and-pencil
surveys. However, surveys are also conducted over the phone or through e-mail. Increasingly,
web-based surveys are being used in research. Similar methodology is also used in
applied setting, such as clinical assessment and personnel assessment.

Longitudinal studies

Longitudinal studies are often used in psychology to study developmental trends
across the life span, and in sociology to study life events throughout lifetimes
or generations. The reason for this is that unlike cross-sectional studies, longitudinal
studies track the same people, and therefore the differences observed in those people
are less likely to be the result of cultural differences across generations. Because
of this benefit, longitudinal studies make observing changes more accurate and they
are applied in various other fields.

Because most longitudinal studies are observational, in the sense that they observe
the state of the world without manipulating it, it has been argued that they may
have less power to detect causal relationships than do experiments. They also suffer
methodological limitations such as from selective attrition because people with
similar characteristics may be more likely to drop out of the study making it difficult
to analyze.

Some longitudinal studies are experiments, called repeated-measures experiments.
Psychologists often use the crossover design to reduce the influence of confounding
covariates and to reduce the number of subjects. Observation in natural
settings

Phineas P. Gage survived an accident in which a large iron rod was driven completely
through his head, destroying much of his brain's left frontal lobe, and is remembered
for that injury's reported effects on his personality and behavior.

In the same way Jane Goodall studied the role of chimpanzee social and family life,
psychologists conduct similar observational studies in human social, professional
and family lives. Sometimes the participants are aware they are being observed and
other times it is covert: the participants do not know they are being observed.
Ethical guidelines need to be taken into consideration when covert observation is
being carried out.

Qualitative and descriptive research

Research designed to answer questions about the current state of affairs such as
the thoughts, feelings and behaviors of individuals is known as descriptive research.
Descriptive research can be qualitative or quantitative in orientation. Qualitative
research is descriptive research that is focused on observing and describing events
as they occur, with the goal of capturing all of the richness of everyday behavior
and with the hope of discovering and understanding phenomena that might have been
missed if only more cursory examinations have been made.

Neuropsychological methods

Neuropsychology seeks to connect aspects of behavior and mental activity with the
structure and function of the brain. Cognitive neuropsychology and cognitive neuropsychiatry
study neurological or mental impairment in an attempt to infer theories of normal
mind and brain function. This typically involves looking for differences in patterns
of remaining ability (known as "functional disassociations") which can give clues
as to whether abilities are composed of smaller functions, or are controlled by
a single cognitive mechanism.

In addition, experimental techniques are often used to study the neuropsychology
of healthy individuals. These include behavioral experiments, brain-scanning or
functional neuroimaging, used to examine the activity of the brain during task performance,
and techniques such as transcranial magnetic stimulation, which can safely alter
the function of small brain areas to reveal their importance in mental operations.

Computational modeling

Computational modeling is a tool often used in mathematical psychology and cognitive
psychology to simulate a particular behavior using a computer. This method has several
advantages. Since modern computers process extremely quickly, many simulations can
be run in a short time, allowing for a great deal of statistical power. Modeling
also allows psychologists to visualize hypotheses about the functional organization
of mental events that couldn't be directly observed in a human.

Several different types of modeling are used to study behavior. Connectionism uses
neural networks to simulate the brain. Another method is symbolic modeling, which
represents many different mental objects using variables and rules. Other types
of modeling include dynamic systems and stochastic modeling.

Animal studies

Animal learning experiments aid in investigating the biological basis of teaching,
memory and behavior. In the 1890s, Russian physiologist Ivan Pavlov famously used
dogs to demonstrate classical conditioning. Non-human primates, cats, dogs, pigeons,
rats and other rodents are often used in psychological experiments. Ideally, controlled
experiments introduce only one independent variable at a time, in order to ascertain
its unique effects upon dependent variables. These conditions are approximated best
in laboratory settings. In contrast, human environments and genetic backgrounds
vary so widely, and depend upon so many factors, that it is difficult to control
important variables for human subjects. Of course, there are pitfalls in generalizing
findings from animal studies to humans although animal models can be helpful in
developing an understanding of human behavior (e.g., addiction research).

Criticism

Theory

Criticisms of psychological research often come from perceptions that it is a "soft"
science. Philosopher of science Thomas Kuhn's 1962 critique implied psychology overall
was in a pre-paradigm state, lacking the agreement on overarching theory found in
mature sciences such as chemistry and physics.

Because some areas of psychology rely on research methods such as surveys and questionnaires,
critics have asserted that psychology is not an objective science. Other phenomena
that psychologists are interested in, such as personality, thinking, and emotion,
cannot be directly measured and are often inferred from subjective self-reports,
which may be problematic.

Misuses of hypothesis-testing in psychology, and the use of hypothesis testing at
all is controversial. Research[which?] has documented that many psychologists confuse
statistical significance with practical importance. Statistically significant but
practically unimportant results are common with large samples.[65] Some psychologists
have responded with an increased use of effect size statistics, rather than sole
reliance on the Fisherian p < .05 significance criterion (whereby an observed difference
is deemed "statistically significant" if an effect of that size or larger would
occur with 5% (or less) probability in independent replications, assuming the truth
of the null-hypothesis of no difference between the treatments).

Sometimes the debate comes from within psychology, for example between laboratory-oriented
researchers and practitioners such as clinicians. In recent years, and particularly
in the U.S., there has been increasing debate about the nature of therapeutic effectiveness
and about the relevance of empirically examining psychotherapeutic strategies.

Practice

Some observers perceive a gap between scientific theory and its application—in particular,
the application of unsupported or unsound clinical practices. Critics say there
has been an increase in the number of mental health training programs that do not
instill scientific competence. One skeptic asserts that practices, such as "facilitated
communication for infantile autism"; memory-recovery techniques including body work;
and other therapies, such as rebirthing and reparenting, may be dubious or even
dangerous, despite their popularity.[69] In 1984, Allen Neuringer had made a similar
point[vague] regarding the experimental analysis of behavior.

Current ethical standards of psychology would not permit the following studies to
be conducted today. These human studies would violate the Ethics Code of the American
Psychological Association, the Canadian Code of Conduct for Research Involving Humans,
and the Belmont Report. Current ethical guidelines state that using non-human animals
for scientific purposes is only acceptable when the harm (physical or psychological)
done to animals is outweighed by the benefits of the research. Keeping this in mind,
psychologists can use on animals research techniques that would not necessarily
be performed on humans.

• An experiment by Stanley Milgram raised questions about the ethics of scientific
experimentation because of the extreme emotional stress suffered by the participants.
It measured the willingness of study participants to obey an authority figure who
instructed them to perform acts that conflicted with their personal conscience.

• Harry Harlow drew condemnation for his "pit of despair" experiments on rhesus
macaque monkeys at the University of Wisconsin–Madison in the 1970s. The aim of
the research was to produce an animal model of clinical depression. Harlow also
devised what he called a "rape rack", to which the female isolates were tied in
normal monkey mating posture.In 1974, American literary critic Wayne C. Booth wrote
that, "Harry Harlow and his colleagues go on torturing their nonhuman primates decade
after decade, invariably proving what we all knew in advance—that social creatures
can be destroyed by destroying their social ties." He writes that Harlow made no
mention of the criticism of the morality of his work.

University psychology departments have ethics committees dedicated to the rights
and well-being of research subjects. Researchers in psychology must gain approval
of their research projects before conducting any experiment to protect the interests
of human participants and laboratory animals.

Systemic bias

In 1959 statistician Theodore Sterling examined the results of psychological studies
and discovered that 97% of them supported their initial hypotheses, implying a possible
publication bias. Similarly Fanelli (2010) found out that 91.5% of psychiatry/psychology
studies confirmed the effects they were looking for, which was around five times
more often than in space- or geosciences. Fanelli argues that this is because of
researchers in "softer" sciences have fewer constraints to their conscious and unconscious
biases.

In 2010, a group of researchers reported a systemic bias in psychology studies towards
WEIRD ("western, educated, industrialized, rich and democratic") subjects. Although
only 1/8 people worldwide fall into the WEIRD classification, the researchers claimed
that 60–90% of psychology studies are performed on WEIRD subjects. The article gave
examples of results that differ significantly between WEIRD subjects and tribal
cultures, including the Müller-Lyer illusion.